Tool dressing machine



pril 23, 1959 w. MCKAIN 2,883,887

TOOL DRESSING MACHINE 3 Sheets-Sheet 1 Filed Nov. 13, 1956 INVENTOR v Walter P. McKoin V Z ymu/ gw 28, w QCKAIN TOOL DRESSING MAQIHINE Filed Nov. 13, 1956 5 Sheets-Sheet 2 Fig.6.

INVENTOR Walter P. McKcin 3 Sheets-Sheet 3 Filed Nov. 15, 1956 i v I v INVENTCR Walter P. Mc Kain ,TOOLDRESSING MACHINE "Walter P.1MKain, Parkershurg, 'W. Va., 'as'signor, by

. mesne assignments, to Fada'f Radio 82 Electric C0,, Inc., :Cin'cinnati, Ohio, a'corporation of, New York .Application November 113,; 19576,:Serial No; T 621,901

10 Claims. ((1 76-45) ':This invention: relates .to rimprovernents :for :'a tool :dressingtmachine of: Tthe'rkin'd: disclosed-Jimmy 1 copending applicationSerialiNo. l2,764..'filedlJuner2, 1955, now- ;Patent No. 2,832,236. More particularly, this. invention :pertains to improved'features for such'a machine utilizable -in'.the dressing of pointed bits of a kindcommonly em- ;ployed by cabletool drillers.

:Myzimprovements set forth herein are illustrated for use ina unitary machine embodiment ofthe' general type set forth in.my aforesaid copending'application Serial ;No. 512,764' utilizing halved dies and features'setvforth "in my Patent No.'2,767,599. 'My improvements herein may be incorporated to provide a closing operation of a "vertical die cylin'derat asufficient but lower closing pres- ;sure' with 1 automatic -application of a higher hold-down pressure to lock at' least a .dressing'die in closed position without necessity for-any hold-down cross bar (compare bar 24 in my aforesaid application Serial No. 512,764); to :tolerate the'presence of scale, particles or'flash trimmings under a die or partthereof; to provi'de compensation against wear caused by rocking movement of the 'die'halvesyto provide a carrier roll mechanism to support'in a cushioned manner the forward end of -a'tool when the dies are open; to provide new'meansfor lifting "dies away from the cross bed to enable such scale, flash trimmings or other particles to be'brushed out; and to provide new pivot and pick-up'means for the die segments.

"Other objects and advantages willbe apparent from 'the'following description and from the'accompanying drawings, which are illustrativeo'f one embodiment'only'of .my "new features, in which: I

Figure'l-is a view in end elevatiomwithsome parts insection and others broken away,from the rear with improvements of this invention. in 'a'machine :of 'my invention as disclosed in my aforesaid application Serial No. "512,764 inclusive of featuresdescribed and "claimed 'inniy Patent No. 2,767,599;

'Figure 2 is a'view in end elevation, with'som'e parts shown in section and othersbroken'away, taken along -lineII-.II of Figure 1;

Figure 3 is "a plan view, with some parts shown .in section and others broken away, taken generally along ,line III-III of Figure 2;

Figure 4 he View in section illustrating anew'vertical die cylinder mechanism for an improved Imachine em- .bodiment as illustrated herein;

L'Figure 5 is adetail view .of a portion"ofthel'new "con- -i"dres'sing machine exclusive of the combinative improvements disclosed and claimed 'herein. "Subject-matter' dis- *closed but not claimed herein is claimed in copending application Serial No. 622,162, filed November 14, 1956.

In Figures 1 to 3 hereof, horizontal H-beams'l0 'extend in parallel fashion along the "sides of the-new machine'as principal horizontal members of the'franie 'thereof rigidly joined together at the respectiveends.

The new machine is a self-sufficient unit and maybe mounted on wheels for ease of movement or it may be placed on a foundation in aishop or plant, as I'desird. Vertical H-beams 11 are rigidly connected-at theirrlower ends by welding or otherwise to'the H-beams 10," "the parallel vertical H-beams' 11 being rigidly connected together'across the top 'to'form a"superstructure'J-part of the new'machine from which a'verticaldie cylinder'me'ch- "anism 12 depends'in pivoted relation to suchvsuper'structure to'open and close'a dressing die 13 alone comprising two halves 13, or both such dressing dieand atrimming die comprising halves 14, as shown in Figures 1 arid-2. Filler plates 15 flush with the edges of the flanges z'of H-beams11 on the front and rear sides thereof and plates 15 on the inner sides thereof serve as'guides in the course of upward (opening) and of downward (closing) movement of'a die operating head 16 which is'pivotally connected throughthe medium of spaced brackets 17 to 'a piston rod 18 of cylinder 12, the lower end of piston 'rod'18' being secured in a trunnion block 19 journaled in said brackets 17. A cross bar Ztl'depends below" the H-beams 10 and is rigidly secured thereto. Crossibar 20 is in the form of a strengthmember which serves as a bed on which the halves of each of the dies are adapted to rock. A pair of replaceable hardened steel tracks in the form of wear resistant plates 21 are provided for each of the dies 13 13 and 1414 to engage thebotany extent, they may readily be replaced upon removing the bolts 25 so that new plates 21 can be inserted. Such removal and replacement of the plates 21can be performed by merely lifting the respective die or dies a little above the plates to be so replaced as hereinafter described without taking the dies out'of the machine.

Each of the die halves is provided with upward projec- 'tions 26 in the case of halves 13 and with upward projections 27 in the case'of halves 14. Such upward-projections 26 and 27, when the dies are closed, respectively 'fit into upwardly extending tapered openings 28 and 29,

respectively, the more massive of the downward and upward projections belonging to the dressing die l3-13 which must withstand the heavy hot forging rolling pressure of a dressing roll against the face of a preheated tool bit'Stl placed in the machine for such dressing and for trimming. When the dressing and trimming dies are operated together, an operating lever 31 is in the position shown so that a latch 32 at each end ofshaft-"33 "overlies and holds its respective trimming die operating arm 34 down against and as a part of head 16 as 'shown --dies by'the raising of head 16 due to there-tractionbf piston' 'rod 18 into cylinder 12 will also raise the--arms"34 "and'ppen 'the'halves of the trimming die 14- 14 as th' e assess? halves of the dressing die 13-13 are also being opened. However, if with the latch 32 thus in inoperative position, head 16 is moved downwardly from its top or die open" position by the extension of piston rod 18, the inner ends of arms 34 will follow head 16 because of the pivotal connections 34a therewith while the outer ends of arms 34 will remain above head 16 in view of the pivotal connection 341) between arms 34 and links 36 respectively leaving the trimming die halves 14 open despite the fact that the downward movement of head 16 nevertheless causes the halves 13 to close so that the projections 26 can enter the forward slot 255.

Head 16 is pivotally connected to the upper end of the die halves 13 by a pair of links 35 in the manner set forth in my aforesaid patent; while the arms 34 are pivotally connected to the upper ends of the die halves 14 in like manner by the links 36. The respective pairs of links 35 and 36 at their inners ends are pivotally connected to the respective die halves by a headed pivot bolt 37 in a manner which also forms a feature of this invention, as more fully exemplified in Figure 6. Therein, a hole 38 is drilled into each projection 26 and each projection 27 parallel to the axis of the respective die. A recess 3% capable of accommodating a nut 4i) somewhat loosely therein is also provided in the upward projection so that the nut can be inserted from the inner vertical edge 41 of the die half until the threaded hole 42 in nut an is in registry with opening 38. Thereupon, bolt 37, which has a recessed socket 43 for a socket wrench in its head, is passed through an opening 44 in the respective link, so that the unthreaded portion of the shank of bolt 37 cooperates and serves as a. pivot journal for such link. The threaded end 45 of bolt 37 engages the threads of the nut 46} and bottoms at the inner end of hole 38. Hence, as bolt 37 is tightened, it will draw nut an toward the head of bolt 37 and jam it against the adjoining face of recess 39 to provide a lock nut result which will keep pivot bolt 37 firmly held against loosening during the course of all operations of my machine and yet permit pivot bolt 37 to be loosened with a wrench whenever the die half is to be removed readily as in the course of a replacement thereof after a large number of die operations on tool bits being dressed and trimmed.

In removing one or more of the die halves, the head 16 is raised by the retraction of rod 13 to open the die halves 13l3 and lid-14, the respective die halves to each side of the longitudinal center of the machine resting, when the dies are opened, against the frame angles 46 fixed to gusset plates 46:: welded to beams 10, as shown by the dotted outline of a die segment 14 in Figure 1. Thereupon, the pivot bolts 37 may be removed freeing the die halves from any mechanical link to the balance of the machine. Each of the die halves may be provided with a longitudinal hole 47 extending through it. Thus, when there is no tool bit in the machine, a rod or mandrel attached to a chain hoist or other materials handling equipment can be passed through the hole 47 in any die half to be removed so as to lift that die half until the downward projection thereof clears the respective slot 22 whereupon the die halfoan be removed by further lifting toward the open por tion of the machine to the rear of the superstructure. Reversal of such steps will enable any die half or halves to be replaced and mechanically reconnected as an operative part of the machine.

Front hangers 48 are welded to the front of head 16 and depend below it, while rear hangers 49 are welded to the respective arms 34 and depend therefrom. The hangers i8 and 49 on each side of the longitudinal center of the machine are provided with a hole 50 in registry. Thereby, when the apparatus is in the position shown in Figures 1 and 2, irrespective of which position operating lever 31 is in, a pin can be passed through such registering holes 50 on each side of the longitudinal center of the machine so that if rod 18 is raised, such pins, one of which is shown in chain-line out-line as 51 in Figure 2, will keep the linkages 3536, the head 16 and the arms 34 in the position shown in Figure 1 and lift projections 23 and 24 out of the slots 22 as rod 18 is retracted. Such a lift of even a few inches will enable a workman to sweep any scale, flash trimmings or other particles off the plates 21 and out from underneath the respective dies, thereby relieving any tendency of such foreign bodies to cause any die or part thereof to be somewhat misaligned relative to another. After the dies are reseated with the downward projections in the slots 22, the pins 51 are withdrawn and the machine is again ready, without any material delay having occurred, for continued dressing and trimming operations.

A further feature and object of this invention is to provide a relatively lower force in the course of most of the closing movement of piston rod 18 by the downward or closure stroke thereof out of cylinder 12, which force will not-increase to locking or hold-down force on head 16 unless and until the dressing die 13-13, or both the dressing and trimming dies l3-13 and 14-44, as the case may be, are fully closed with the upward projections thereof in the upwardly tapered opening 28, or in both 28 and 29, as the case may be. Should some obstruction be encountered which prevents the die or dies'from fully closing, cylinder 12 will not exert damaging force with the result that when the trouble is observed, it can be remedied without harm having occurred in the meantime to my machine. In the accomplishment of such last-mentioned feature, I provide a new vertical die cylinder mechanism for the die cylinder 12. Such cylinder may be provided with an upper cylinder end or head 52 and a lower cylinder end or head 53 between which a piston 54 is reciprocated in the course of opening and closing operations of the die halves, suitable seals being provided including a packed stufling box 55 at the rod end of the cylinder 12. The piston 54 is moved in a doWnward or die closing direction by the admission of hydraulic liquid under pressure into an upper port 56; hydraulic liquid on the rod side of piston 54 being exhausted through a lower port 57. Conversely when piston 54 is to be moved in an upward or die opening direction, bydraulic liquid under pressure is admitted through port 57 into the rod end of the cylinder and the liquid in the head end of piston 54 is exhausted through port 56. Such hydraulic liquid may be supplied through flexible pressure hoses by any suitable hydraulic circuit means including operating lever controls to regulate the admission of hydraulic liquid under pressure into the head end or rod end of the cylinder 12 as desired, as will be well known by those having skill in the hydraulic circuit art to Whom this invention is disclosed.

Upper cylinder head 52 is provided with a projecting lug 58 which fits between brackets on the superstructure so that a journal can be passed through such brackets and through opening 59 in lug 5% to pivotally suspend cylinder 12 from such superstructure supported by the H-bearns 11, the axis of the journal through lug 58 preferably being parallel to the axis of the trunnion block 19 afiixed to the lower end of piston 18. The upper end 60 of piston rod 18 is threaded for engagement by a central threaded opening through piston 54 as shown in Figures 4 and 5. The upper end of piston rod 18 is also provided with a central bore 61 extending part of the way down from the top. Lateral passages 62 extend radially from the outside of piston rod l8 adjacent the underside of piston head 54 into central bore 61. The upper end of bore 61 is continued through a center opening 63 in a cap bolt 64 which threadably engages the upper threaded end of bore 61 and is locked to rod 13 by a lock washer 65, a nut 66 in turn locking portion 60 to piston head 54.

A slide valve 67 is slidably positioned in bore 61 and is biased at rest to block off the connection between the passages 62 andbore 61 as shown in Figure 5, a coil spring 68' in the bottom of bore 61 surrounding a guide 69 on the underside of valve 67, said spring being selected to regulate the pressure which must be exerted to depress valve 67 sufliciently to establish communication between the passages 62 and bore 61 in a downward stroke of rod 18. Valve 67 has a necked portion 70 of reduced diameter between its top extremity 71 and its bottom flange 72. The top extremity 71'is beveled to fit tightly against the bottom edge 73 of bolt 64 and thereby close any passage through bore 61 to the head end of piston 54 during an upward die opening stroke of rod 18 in the course of its retraction. H

If we assume that the new die cylinder construction illustrated in Figures/l and 5 is inthe position shown in Figure 4 and it is desired to move head 16 downwardv to close at least the dressing die 13-13, hydraulic liquid under pressure is admitted to port 56 and will flow into the head end of cylinder 12 and will be exerted through opening 63 and bore 61 and will depress valve 67 when the force thereof exceeds the strength of spring 68 uncovering the radial passages 62 so that a portion of the hydraulic liquid entering port 56 is by-passed to the rod side of piston 54 from whence it is exhausted through port 57. Since spring 68 is selected to provide but a relatively small opposing force of a magnitude sufficient to initiate and continue downward movement of piston 54, such by-passing limits the closure force exerted on piston 54 in the course of its downward movement with the result that if an obstruction should be encountered, at such relatively lower closing force, all of the liquid would by-pass through the passages 62 to exhaust 57 and prevent rupture or breaking of parts of my machine which might otherwise be caused by such obstruction if the full pressure of the hydraulic liquid were exerted on piston 54 before the die or dies were about fully closed. In the final portion ofsiich die closure stroke, the outer ends of the passages 62 start to enter a close fitting bore in a bushing block 74 shutting on the hydraulic liquid bypass through passages 62 and tremendously increasing the force exerted on piston 54 and head 16 in the relatively small final closure movement of my new cylinder mechanism and of head 16. That final closure force is suflicient in my new die cylinder construction to act by itself as a hold-down for the closed dressing die 13-13, and for the trimming die 14-14 if that too is closed at the same time, without requiring any special hold-down cross bar for the dressing die as incorporated in earlier forms of my tool dressing machine. More over, since such hold-down is hydraulic, it will accom modat the presence, for example, of unevenness owing to particles which may have fallen underneath the dies and moved one or more of them or of their parts some what relative to the others without adverse effect upon the operation. I

In the upward or die" opening movement of piston 54, as soon as the passages 62 emerge from the bushing block 74, the hydraulic liquid under pressure entering port 57 will move slide valve 67 upwardly until a relatively tight connection is established between its top 71 and edge 73 to block passage of liquid through bore 61 from the rod end to the head end of piston 54 I In this invention, I have also provided new carrier r'oll mechanism 75 to support the bit end of a tool being dressed both before it is engaged by the dies and after it has been engaged by the dies. The dies are hardened aiid if the bit end of a tool, like tool 30, should strike or be dragged across one of the hardened portions of either of the dies 13-13 or 14-14, damage to the tool may result. In the carrier roll mechanism, a bracket 76 is rigidly fastened to the rear edge of bed plate 20 and has ears 77 and 78 which are transversely drilled in registry. A torsion rod 79 extends through the openings in ears 77 and 78 where it is bushed. A sleeve .81 is also bushed and has rod 79 extending freely therethrough to the end 6 of said sleeve'adjacent car 78 at which pointslceve 81 is fixed-to rod 79 by shear pins 82 extending through sleeve: 81- at that point and rod 79. Sleeve 81 carries rigid-arms 83 extending rearwardly to support a carrier roll 84 having a dished center 85, the carrier rollbeing mounted'on a-shaft, the ends of-which' shaft are journaled in the outer end of the carrier roll arms 83.

A hydraulic cylinder 86 is pivotally connected to a bracket 87 to one side of my new machine andhas a' piston therein which moves a plunger 88 to the desired extent in the desired direction by means of the admission ofhydraulic liquid applied through a suitable operating,

lever control as will be understood by one skilled in the art, either through'port' 89 or 90 depending upon what direction and angle ofmovement is desired of carrier roll 84.; The-cylinder preferably has ahydraulic-l o'ck in the circuit thereof to fix that position of plunger 8810 which it may be moved by such control. An end of torsion rod 79 is threaded at 91 so that it may engage and be secured to a clevis 92. A clevis block- 93 is piv otally mounted in clevis 92- and has a drilled and tapped opening 94 to receive a threaded adjustment rod 95. The: rear end of adjustment rod 95 is affixed to a capstan 9 6 which in turn is immovably secured to the outer end of plunger 88 by a keying pin 97. Radially extending wrench openings 98 are provided in capstan 96 circumferentially spaced around the periphery thereof so that the capstan 96 may be turned to raise or lower carrier roll 84 as indicated in Figures 1 and 2 to accommodate tools having different diameters. Moreover, the torsion character of the connectionbetween carrier roll 84 and the clevis end thereof enables carrier roll 84 to absorb in a cushioning manner the tolerance in diameters which. exists among tool bits of the same nominal diameter and size without requiring that an adjustment be made by turn: ing capstan 96. When the dies are open, carrier roll 84 will support any such tool, like tool 30, in position to be inserted into or withdrawn from the open dies withoutdamage to the tool-bit or to the dies. Thus, the workman operating cylinder 86 would see to it that carrier roll 84 is up in a. carrying position such as shown in solid lines in Figure 2 and in dash-and-dot lines in Figure l for the given size tool being dressed whenever the dies are open or about to be opened. Moreover, with such carrier roll. 84 in tool supporting position as shown in Figure 2 with tool 30 thereon, any desired longitudinal adjustment of the tool may be obtained as set forth, for example, in my aforesaid application Serial No. 512,764, or as setforth in my copending application Serial No. 560,650, filed January 23, 1956, while the longitudinal movement of the tool moving carriage itself may be obtained by rotation of the lead screws 80 on each side of the frame adjacent H-beams 10 in the desired direction of rotation of such lead screws for such movement.

Various modifications may be made in the illustrated.

embodiment having the novel features disclosed herein. without departing from the spirit of my invention or the scope of the appended claims.

I claim:

1. In a tool dressing machine, apparatus comprising, in combination, a frame including a superstructure, a die cylinder pivotally suspended from said superstructure, apiston in said cylinder, a piston rod connected to said piston and extending through the lower end of said cylinder, a bore in the upper end of said piston rod, passages adjacent the rod side of said piston extending between said bore and the rod end of said cylinder, a slide valve in said bore, a die operating head pivotally connected to the lower end of said piston rod, ports respectively for the head and rod ends of said cylinder, a spring in said bore between slide valve and the lower portion of said bore normally positioning said slide valve across the inner ends of said passages, a seat at the upper end of said bore adapted to cooperate with the top of said slide valve during an upward opening movement of said piston, said slide aesassr valve being adapted to open said' passages during a downward closing movement of said piston for the greater part of the downward stroke of said piston whensaid slide valve is subjected to a force greater than that of said spring, and a bushing block adapted to close the outer ends of said passages in the final portion of said downward stroke of said piston to increase the force to which said piston is subjected to hold said dies down in closed position by means of said cylinder.

2. In a tool dressing machine, apparatus comprising, in combination, a frame, a substantially vertical die operating cylinder connected to said frame, a piston in said cylinder, a piston rod connected to said piston and extending through the lower end of said cylinder, a bore in the upper end of said piston rod extending between the respective rod and head end sides of said piston, said rod further having transverse passages extending between said bore and said rod end side of said piston, slide valve means in said bore normally shutting off communication between said rod and head ends by closing the inner ends of said transverse passage, means at the upper end of said bore adapted to cooperate with said slide valve means to close said bore during an upward opening movement of said piston, said slide valve means being adapted to provide communication between said rod and head ends through said passages during a predetermined downward closing pressure against the head end of said piston, and means adapted to close the outer ends of said passages in the final portion of a downward stroke.

3. In a tool dressing machine, apparatus comprising, in combination, a frame including a superstructure, a die opening and closing cylinder pivotally suspended from said superstructure, a piston rod extending through the lower end of said cylinder, a die operating head connected to said piston rod, a die split generally vertically into halves, a cross bar bed plate rigidly connected to said frame on which said halves of said die are adapted to rock, links pivotally and respectively connected between said halves of said die and said head, and replaceable tracks secured to said bed plate between the same and said die halves.

4. In a tool dressing machine, apparatus comprising, in combination, a frame, a substantially vertical die operating cylinder connected to said frame, a piston in said cylinder, a piston rod connected to said piston and extending through the lower end of said cylinder, a bore in the upper end of said piston rod extending between the rod and head ends of said cylinder, slide valve means in said bore normally closing off communication between said rod and head ends, means at the upper end of said bore adapted to cooperate with said slide valve means during an upward opening movement of said piston, said slide valve means being adapted to provide communication between said rod and head ends during a downward closing movement of said piston for the greater part of its downward stroke, a die operating head connected to said piston rod, a die split generally vertically into halves, a cross bar bed plate rigidly connected to said frame on which said halves of said die are adapted to rock, link connections between said halves of said die and said head, and wear plates secured to said bed plate between the same and said die halves.

*5. In a tool dressing machine, apparatus comprising, in combination, a frame including a superstructure, a die opening and closing cylinder pivotally suspended from said superstructure, a piston rod extending through the lower end of said cylinder, a'die operating head connected to said piston rod, a die split comprising two generally vertically divided halves, a cross bar bed plate rigidly connected to said frame on which said halves of said die are adapted to be rocked between open and closed positions, pivotal connections between said halves of said die and said head, a carrier roll having a center of reduced diameter positioned adjacent and to the rear of said die, an angularly adjustable torsion rod connected to said carrier roll to raise and lower it, and means whereby said torsion rod and carrier roll can be elevated to a position to support a tool when said dies are open in a cushioned manner.

6. In a tool dressing machine, apparatus comprising, in combination, a frame, a substantially vertical die op erating cylinder connected to said frame, a piston rod extending through the lower end of said cylinder, a die operating head connected to said piston rod, at least one die split generally vertically into segments, removable wear means rigidly connected to said frame to support said segments of said die during opening and closing movements thereof, pivotal connections between said segments of said die and said head, a carrier roll positioned adjacent to said die, and means to elevate said carrier roll to a tool support position.

7. In a tool dressing machine, apparatus comprising, in combination, a frame, a die opening and closing cylinder pivotally suspended from said frame, a piston rod extending through the lower end of said cylinder, a head connected to said piston rod, a die split generally vertically into halves, a bed rigidly connected across said frame on which said halves of said die are adapted to rock, link connections between said halves of said die and said head, hangers operatively connected to said head and extending below said links when said links are in die closure position, said hangers having registering openings in the lowermost positions thereof for the insertion of a pin to be passed therethrough beneath said links, whereby when said piston rod is raised to raise said head, said die is raised away from said bed so that particles may be brushed off said bed.

8. In a tool dressing machine, apparatus comprising, in combination, a frame including a superstructure, a die opening and closing cylinder pivotally suspended from said superstructure, a piston rod extending through the lower end of said cylinder, a die operating head connected to said piston rod, a dressing die split generally vertically into halves, die operating arms pivotally connected to said die operating head, means to detachably connect said die operating arms in unitary manner to said head, a trimming die split generally vertically into halves and in longitudinal registry with and to the rear of said dressing die, a cross bar bed plate rigidly connected to said frame on which said halves of said dies are adapted to rock, links connected respectively between said head and said dressing die halves and between said arms and said trimming die halves, hanger means respectively depending from said head and said arms and extending below the links on each side of the longitudinal center of said machine when said links are in die closure position, registering openings through the respective hangers on each such side adapted to receive pins, whereby when said piston rod is retracted said head and arms are lifted to lift said respective dies above said bed plate, said die halves further having longitudinal holes adapted to be engaged for die positioning in and removal from said machine.

9. In a unitary tool dressing machine, apparatus comprising, in combination, a frame including a superstructure, a die opening and closing cylinder pivotally suspended from said superstructure, a piston rod extending through the lower end of said cylinder, a die operating head connected to said piston rod, a dressing die split generally vertically into halves, arms pivotally connected to said die operating head, means to connect said die operating arms in unitary manner to said head, a trimming die split generally vertically into halves and in longitudinal registry with and to the rear of said dressing die, a cross bar bed plate rigidly connected to said frame on which said halves of said dies are adapted to rock, removable wear plates positioned between said dies and said bed plate, links pivotally connected respectively between said head and said dressing die halves and between said die operating arms and said trimming die halves, locknut means for said pivotal connections between said links and said die halves respectively, hanger means respectively depending from said head and said die operating arms and extending below the links on each side of the longitudinal center of said machine when said links are in die closure position, registering openings through the respective hanger on each such side adapted to receive pins whereby when said piston rod is retracted said head and die operating arms are lifted to lift said respective dies above said bed plate and means for moving said piston rod in a downwardly die closing direction under one force from the initiation nearly to the end of a die closure stroke of said piston rod and at a greater force during the final portion of the closure stroke of said piston rod.

10. In a tool dressing machine, apparatus comprising, in combination, a frame including a superstructure, a die opening and closing cylinder pivotally suspended from said superstructure, a piston rod extending through the lower end of said cylinder, a die operating head connected to said piston rod, a die split generally vertically into halves, a cross bar bed plate rigidly connected to said frame on which said halves of said die are adapted to 10 rock, links pivotally and respectively connected between said halves of said die and said head, said die halves being recessed transversely inwardly from the inner side thereof, a longitudinal opening intersecting said recess and projecting beyond for a portion of the longitudinal depth of said die half, a pivot bolt having a smooth shank and a threaded end, a lock nut adapted to be inserted into said recess to engage said threaded end of said pivot bolt after said pivot bolt is passed freely through a pivot opening in a respective one of said links, said hole having a length such that the inner end of said bolt is in binding engagement with the inner end thereof when said bolt is tightened to jam said nut into locking engagement with said recess.

References Cited in the file of this patent UNITED STATES PATENTS 

